Almost blank subframe based orthogonal resource allocation in a wireless network environment

ABSTRACT

An example method for facilitating almost blank sub-frame (ABS) based orthogonal resource allocation in a wireless network environment is provided and includes receiving at a serving Evolved Universal Terrestrial Radio Access Network (E-UTRAN) nodeB (eNB), ABS patterns from a plurality of neighboring eNBs in a orthogonal frequency-division multiplexing based network, each neighboring eNB transmitting a separate ABS pattern, setting a maximum duty cycle of physical downlink control channel in a frame to be transmitted by the serving eNB within its serving cell, and computing an optimal ABS pattern at the serving eNB subject to the maximum duty cycle and based on the ABS patterns received from the plurality of neighboring eNBs. In specific embodiments, computing the optimal ABS pattern includes identifying neighboring eNBs transmitting at each sub-frame of the frame, identifying sub-frames transmitted by a least number of neighboring eNBs, and selecting each identified sub-frame for configuring as an ABS.

RELATED APPLICATION

This Application is a continuation (and claims the benefit of priorityunder 35 U.S.C. § 120) of U.S. application Ser. No. 14/261,812, filed onApr. 25, 2014, entitled “ALMOST BLANK SUBFRAME BASED ORTHOGONAL RESOURCEALLOCATION IN A WIRELESS NETWORK ENVIRONMENT,” Inventors TakahitoYoshizawa, et al., which Application is a continuation (and claims thebenefit of priority under 35 U.S.C. § 120) of U.S. application Ser. No.14/261,566, filed Apr. 25, 2014, entitled “ALMOST BLANK SUBFRAME BASEDORTHOGONAL RESOURCE ALLOCATION IN A WIRELESS NETWORK ENVIRONMENT,”Inventors Takahito Yoshizawa, et al. The disclosure of the priorapplications are considered part of (and are incorporated by referencein) the disclosure of this application.

TECHNICAL FIELD

This disclosure relates in general to the field of communications and,more particularly, to almost blank sub-frame (ABS) based orthogonalresource allocation in a wireless network environment.

BACKGROUND

Orthogonal frequency-division multiplexing (OFDM) is a method ofencoding digital data on multiple carrier frequencies. OFDM is a popularscheme for wideband digital communication (both wired and wireless) inapplications such as digital television and audio broadcasting, digitalsubscriber line (DSL) Internet access, wireless networks, power-linenetworks, and 4G mobile communications, such as Long Term Evolution(LTE). LTE, marketed as 4G LTE, is a standard for wireless communicationof high-speed data for mobile phones and data terminals based on theGlobal System for Mobile Communications (GSM)/Enhanced Data rates forGSM Evolution (EDGE) and Universal Mobile Telecommunications System(UMTS)/High Speed Packet Access (HSPA) network technologies. The LTE andrelated standards are developed by 3rd Generation Partnership Project(3GPP). LTE uses Evolved Universal Terrestrial Radio Access Network(E-UTRAN) radio access network standard for LTE's air interface system.The 3GPP infrastructure provides wired or wireless connections amongcommunicating intermediate stations, called E-UTRAN nodeBs (eNBs). LTEis accompanied by an evolution of non-radio aspects under SystemArchitecture Evolution (SAE), which includes the Evolved Packet Core(EPC) network. LTE and SAE together comprise the Evolved Packet System(EPS).

BRIEF DESCRIPTION OF THE DRAWINGS

To provide a more complete understanding of the present disclosure andfeatures and advantages thereof, reference is made to the followingdescription, taken in conjunction with the accompanying figures, whereinlike reference numerals represent like parts, in which:

FIG. 1 is a simplified block diagram illustrating a communication systemfor facilitating ABS based orthogonal resource allocation in a wirelessnetwork environment;

FIG. 2 is a simplified block diagram illustrating example details of anembodiment of the communication system;

FIG. 3 is a simplified block diagram illustrating yet other exampledetails of an embodiment of the communication system;

FIG. 4 is a simplified block diagram illustrating yet other exampledetails of an embodiment of the communication system;

FIG. 5 is a simplified flow diagram illustrating example operations thatmay be associated with an embodiment of the communication system;

FIG. 6 is a simplified flow diagram illustrating other exampleoperations that may be associated with an embodiment of thecommunication system;

FIG. 7 is a simplified flow diagram illustrating yet other exampleoperations that may be associated with an embodiment of thecommunication system;

FIG. 8 is a simplified flow diagram illustrating yet other exampleoperations that may be associated with an embodiment of thecommunication system; and

FIG. 9 is a simplified flow diagram illustrating yet other exampleoperations that may be associated with an embodiment of thecommunication system.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Overview

An example method for facilitating ABS based orthogonal resourceallocation in a wireless network environment is provided and includesreceiving at a serving eNB, ABS patterns (e.g., an ABS pattern comprisesa temporal location, or sub-frame indices of ABSs in each frame) from aplurality of neighboring eNBs in a orthogonal frequency-divisionmultiplexing (OFDM) based network, each neighboring eNB transmitting aseparate ABS pattern, setting (e.g., assigning, configuring,determining, computing, calculating, etc.) a maximum duty cycle ofphysical downlink control channel (PDCCH) in a frame to be transmittedby the serving eNB within its serving cell, and computing an optimal ABSpattern at the serving eNB subject to the maximum duty cycle and basedon the ABS patterns received from the plurality of neighboring eNBs.

Example Embodiments

Turning to FIG. 1, FIG. 1 is a simplified block diagram illustrating acommunication system 10 for facilitating ABS based orthogonal resourceallocation in a wireless network environment in accordance with oneexample embodiment. FIG. 1 illustrates a OFDM based network 12comprising cells 14(1), 14(2) . . . 14(N), served by corresponding eNBs16(1), 16(2) . . . 16(N). Note that network 12 can include any number ofcells within the broad scope of the embodiments. A user equipment (UE)18 in cell 14(1) may be enabled to wirelessly communicate in network 12by serving eNB 16(1). Each eNB 16(1), 16(2) . . . 16(N) may beconfigured with respective ABS modules 20(1), 20(2) . . . 20(N).

According to 3GPP specifications, a cell (e.g., 14(1), 14(2) . . .14(N)) is a geographical area that can be identified by a UE (e.g., UE16) based on a (cell) identification that is broadcast from a UTRANaccess point (e.g., executing at eNB 16(1)). The UTRAN access point isassociated with one specific cell; thus there exists one UTRAN accesspoint for each cell. The UTRAN access point is the UTRAN-side end pointof a radio link. The radio link is a logical association between asingle UE and a single UTRAN access point. Its physical realizationcomprises one or more radio bearer transmissions. Each eNB 16(1) . . .16(N) comprises a logical node responsible for radiotransmission/reception in one or more cells to/from UE 18 (and other UEsin network 12). For example, each eNB 16(1)-16(N) can cover multiplecells within a 120° angle. UE 18 comprises a mobile equipment with oneor several UMTS Subscriber Identity Module(s), which includesinformation to uniquely identify a subscriber (e.g., user).

In various embodiments, serving eNB 16(1) may determine a PDCCH dutycycle and ABS pattern for resource allocation in cell 14(1), andcommunicate the information to eNB 16(2) through a suitable X2 message(e.g., message over an X2 interface between two communicating eNBs).Resource allocation refers to configuring resources (e.g., signalcarriers in frequency and time domain) for enabling radio communicationby UE 18 (and other UEs) in network 12. In 3GPP LTE, one Resource Block(RB) comprises 12 consecutive, contiguous sub-carriers (e.g., 15 kHzapart) in the frequency domain. The smallest modulation structure (unitof resource) in LTE is a Resource Element. The Resource Element (RE) isone sub-carrier during one symbol interval (i.e., one symbol long and 1sub-carrier wide). REs aggregate into RBs. Each RB has dimensions ofsub-carriers by symbols (i.e., x symbols long and y sub-carriers widefor an xy sized RB). In some scenarios, twelve consecutive sub-carriersin the frequency domain and six or seven symbols in the time domain formeach RB. Thus, for example, each RB can include 72 or 84 REs.

In the time domain, one radio frame (also referred to herein simply as“frame”) is 10 milliseconds long and comprises several (e.g., 10) 1millisecond sub-frames. The sub-frame is a fundamental communicationunit that carries control signal and user data. Each sub-frame comprisestwo 0.5 ms slots. In the time domain, one slot is exactly one RB long.The RB can comprise 72 or 84 REs for the duration of a 0.5 ms slot.Multiple resource blocks are assigned consecutively in the frequencydomain to a UE in the uplink whereas dispersed, non-consecutiveassignment is done on the downlink. As used herein, “ABS” is a sub-framewith reduced power on some physical channels and/or reduced activity.

In various embodiments, X2 message 22 can enable time domain ABSresource allocation by eNBs 16(1) . . . 16(N) to minimize interferencefor UE 18. According to various embodiments, ABS modules 20(1) . . .20(N) can facilitate an optimal allocation of a temporal location ofABSs (i.e., ABS pattern) in a frame taking into account cell-specificimpact of neighboring cells. Further, ABS modules 20(1) . . . 20(N) cansemi-statically adjust the PDCCH duty cycle (e.g., a percentage of oneframe in which the PDCCH is active) by taking into account thecorresponding eNB's own cell load and traffic demands.

For purposes of illustrating the techniques of communication system 10,it is important to understand the communications that may be traversingthe system shown in FIG. 1. The following foundational information maybe viewed as a basis from which the present disclosure may be properlyexplained. Such information is offered earnestly for purposes ofexplanation only and, accordingly, should not be construed in any way tolimit the broad scope of the present disclosure and its potentialapplications.

OFDM is a frequency-division multiplexing (FDM) scheme used as a digitalmulti-carrier modulation method. A large number of closely spacedorthogonal sub-carrier signals are used to carry data on severalparallel data streams or channels. Each sub-carrier is modulated with aconventional modulation scheme (such as quadrature amplitude modulationor phase-shift keying) at a low symbol rate, maintaining total datarates similar to conventional single-carrier modulation schemes in thesame bandwidth. In OFDM, a physical resource comprises two domains:time-domain and frequency-domain. Signals are allocated independently inboth domains. The LTE network, which is described in example embodimentsis a specific example of the OFDM based network.

The LTE frame carries physical channels and physical signals. Channelscarry information received from higher layers. Signals originate at thephysical layer. The framing structure is common to the uplink anddownlink, but the physical signals and physical channels are different.Physical Downlink Shared Channel (PDSCH) is used to transport user data.Physical downlink control channel (PDCCH) is used to carry resourceassignments for UEs (e.g., provide uplink and downlink resourceallocations to UEs). The PDCCH maps onto REs in up to the first threeOFDM symbols in the first slot of the sub-frame. For a bandwidth of 1.4MHz, it is possible to have up to 4 OFDM symbols. Thus, the PDCCHmapping is bandwidth dependent.

In a general sense, each downlink sub-frame can include two regions:control region and data region. The control region size can bedynamically variable. Within the control region, the PDCCH carriesdownlink control information (DCI) messages comprising downlink resourceassignments, uplink resource grants, uplink power control commands, etc.Each control region comprises control channel elements (CCEs), each ofwhich is a nine set of four resource elements known as Resource ElementGroups (REG) (e.g., each CCE is a group of 9 consecutive REGs; each REGis a group of 4 consecutive REs). The data region carries PDSCHinformation.

In LTE, PDCCH signal quality is an important performance factor. PDCCHcarries the upper layer signaling traffic including radio resourcecontrol (RRC) messages and non-access stratum (NAS) messages. The PDCCHsignal quality determines reliability of signaling in the control plane,potentially influencing reliability of the overall user plane, such ashandover (HO) performance and call reliability. The PDCCH signal qualitycan be especially significant at the cell edge where the signal qualitydegrades inversely proportional to the distance between the eNB and theUE and as interference from the adjacent cell(s) increase. Because OFDMAlacks a Soft HandOver functionality as in WCDMA, signal quality from theserving cell can be of prime importance. Improving the control planesignal quality of the serving cell, for example, at cell edges, canimprove the overall performance (of both control plane and user plane).

Inter-cell interference coordination (ICIC) in LTE is used to minimizeinterference at the UE from neighboring cells. According to an ICICscheme, neighboring eNBs use different sets of RBs throughout the cellat any given time (e.g., no two neighboring eNBs use the same resourceassignments for their UEs). The scheme can greatly improve cell-edgesignal-to-interference-plus-noise-ratio (SINR). The disadvantage of thescheme is decrease in throughput throughout the cells, because full RBsare not utilized. In another ICIC scheme, all eNBs utilize a completerange of RBs for centrally located users, whereas no two neighboringeNBs uses the same set of RBs at any given time for cell-edge users. TheX2 interface is used to share the ICIC information between the eNBs.

Enhanced ICIC (eICIC) is typically used in heterogeneous networkscomprising different sized cells (e.g., macro and pico cells). eICICmitigates interference on traffic and control channels. eICIC usespower, frequency and time domain to mitigate intra-frequencyinterference in heterogeneous networks. eICIC uses the ABS, which aremostly control channel frames with very low power and used to coordinateinter-cell interference in the time domain. The ABS typically does notcontain either PDCCH or PDSCH information. During ABS, the transmittingeNB does not transmit PDSCH but, may transmit critical control channels,and broadcast and paging information (e.g., for ensuring legacy devicesupport).

In time domain, if a macro cell configures ABS sub-frames, UEs connectedto pico/femto cells within an overlapping coverage of the macro cell cancommunicate data during such ABS frames and avoid interference from themacro cell. In frequency-domain eICIC, control channels and physicalsignals (e.g., synchronization signals and reference signals) ofdifferent cells are scheduled in reduced bandwidths in order to havetotally orthogonal transmission of these signals at different cells.

In a general sense, time domain ABS resource allocation can bechallenging. In a frequency-domain approach to resource allocation, thesignal is allocated to one RE so that no two REs collide across signalsfrom two cells in the same carrier. In a time-domain approach toresource allocation, the signal is allocated to the RE of a carrier fromone cell at any given time so that no two adjacent cells use the same REsimultaneously. By turning the sub-frame into ABS, the PDCCH in ABS canbe removed, thereby avoiding interference contribution to theneighboring cells. However, the ABS cannot carry data, thereby reducingthe throughput. Because ABSs severely penalizes the capacity, its usagehas been reserved primarily for Heterogeneous Networks (HetNets).

In a general HetNet deployment, it is possible to have macrocells,picocells, and femtocells coexisting in the same geographical area. Themacrocell is the aggressor relative to the picocell, (e.g., picocell isthe victim). In the case of femto cells, both macro and pico UEs arevictims of the femto cells due to the fact that femto cells are oftenconfigured to operate in a Close Subscriber Group (CSG) mode. The CSGcell only allows access to UEs which have a valid private subscription.Thus, an unsubscribed UE would not be served. Subsequently, to anunsubscribed UE, a CSG Home eNB (HeNB) would act as a source ofinterference. One way to mitigate interference coming from a HeNB wouldbe for the HeNB to introduce ABS patterns, for example, similar to amacro eNB (MeNB)-picocell eNB (PeNB) case.

For example, the throughput of the pico UEs increases with a largernumber of ABSs configured in each frame of the macro cell. However,increasing the number of ABSs can reduce the available sub-frames forthe macro UEs and thus decrease their throughput. Thus, the appropriateABS ratio (number of ABSs over a total number of sub-frames in a frame)and an ABS pattern (positions of ABSs in each frame) may be consideredto coordinate interference between the macro and pico/femto cells.

In an existing mechanism to optimize ABS use, an initial ABS pattern ischosen by a macro eNB based on a victim pico UE reporting from aneighboring pico eNB; subsequently, the ABS pattern is adjusted based onthe request of the pico eNB and the ABS pattern in stored in the macroeNB. The neighboring macro eNBs may update the stored ABS patterns basedon reports of interfering macro cells from the pico eNB. The informationto update ABS patterns are communicated over the X2 interface.

Communication system 10 is configured to address these issues (andothers) in offering a system and method for facilitating ABS basedorthogonal resource allocation in a wireless network environment.According to an embodiment of communication system 10, serving eNB 16(1)may receive ABS patterns from plurality of neighboring eNBs 16(2)-16(N)in OFDM based network 12, each neighboring eNB 16(2)-16(N) transmittinga separate ABS pattern. Serving eNB 16(1) may set a maximum duty cycleof PDCCH in a frame to be transmitted by serving eNB 16(1) within itsserving cell, and compute an optimal ABS pattern at serving eNB 16(1)subject to the maximum duty cycle and based on the ABS patterns receivedfrom plurality of neighboring eNBs 16(2)-16(N). In specific embodiments,computing the optimal ABS pattern includes identifying neighboring eNBs16(2)-16(N) transmitting at each sub-frame of the frame, identifyingsub-frames transmitted by a least number of neighboring eNBs16(2)-16(N), and selecting each identified sub-frame for configuring asan ABS.

According to various embodiments, a group of cells 14(1)-14(N) innetwork 12 may comprise of two or more cells. Within the group, eachpair of two cells (e.g., cells 14(1) and 14(2)) that cover an adjacentcoverage area can establish an X2 interface between corresponding eNBs(e.g., 16(1) and 16(2)) to directly communicate with each other usingX2AP protocol according to 3GPP specifications. (According to LTEstandards, the eNBs are normally interconnected with each other by meansof an interface known as “X2,” to a Mobility Management Entity (MME) bymeans of an “S1-MME” interface and to a serving gateway (S-GW) by meansof an “S1-U” interface.) In the X2 interface, eNBs 16(1) and 16(2) incells 14(1) and 14(2), respectively, may exchange information useful toachieve and maintain coordination between them for resource allocation.The messages can be used for various purposes, including for effecting aself-organized network (SON).

X2 message 22 may be used to achieve coordination of ABS usage betweentwo eNBs 16(1) and 16(2) in adjacent cells 14(1) and 14(2),respectively, for example, to minimize interference between them duringresource usage optimization. According to an embodiment of communicationsystem 10, eNBs 16(1) and 16(2) in adjacent cells 14(1) and 14(2),respectively, may exchange its own resource allocation in time-domain.Each eNB 16(1) and 16(2) in adjacent cells 14(1) and 14(2),respectively, can express the time-domain resource allocation using abinary bit having a value of 0 or 1 to indicate a resource allocation.For example, a value of “0” for an appropriate region of the RB mayindicate that a given eNB has allocated the ABS in a specific RB, and avalue of 1 for the appropriate region of the RB may indicate that thegiven eNB has not allocated the ABS in the specific RB. Thus, the bitsequence of 0 and 1 can indicate the ABS pattern of the respective cell.

By exchanging the ABS pattern through the bit sequence, two adjacenteNBs (e.g., 16(1) and 16(2)) can acquire knowledge of each other'sresource allocation during a certain time period. Thus, by comparing theABS pattern with its own resource allocation during the same timeperiod, each eNB 16(1)-16(N) can detect any collision of resourceallocation with respect to the adjacent cell. Further, by using theinformation exchanged over the X2 interface, eNBs 16(1)-16(N) cancalculate a chance of collision of resource allocation. Thus, each eNB16(1)-16(N) can adjust its own resource allocation behavior to avoid orminimize resource allocation collision. The ABS pattern exchange andsubsequent adjustment in resource allocation may comprise an iterativeprocess substantially continuously carried out in eNBs 16(1)-16(N), forexample, to achieve and maintain minimal interference.

In an example embodiment, X2 message 22 may comprise a resource statusupdate message according to X2AP specification (3GPP TS 36.423). Thestandard X2AP message format can be expanded in X2 message 22 to carryadditional resource allocation information, for example, to facilitateABS allocation coordination across eNBs 16(1)-16(N). For example, X2message 22 may comprise an X2AP resource status update message thatallows serving eNB 16(1) to evaluate whether or not it can reduce thenumber of ABSs in the frame, thereby increasing its own throughput. Theinformation elements in X2 message 22 can include a downlink ABS status(e.g., specifying a percentage of used ABS resources from within a setof usable ABS resources), and a usable ABS pattern bitmap (e.g.,specifying a set of ABS that neighboring eNB 16(2) can use).

There can be multiple types of information that can be exchanged over X2message 22, for example, to derive resource allocation at local cell14(1). By way of examples, and not as limitations, the information caninclude: 1) interference level; 2) traffic load; and 3) PDCCH dutycycle. eNBs 16(1)-16(N) may also consider their own local informationfor the resource allocation decision. In some embodiments, X2 message 22may comprise a load information message, which includes an ABSinformation Information Element (IE). Within the ABS information IE, anABS Pattern Information Bitmap specifies a sequence of bits, with ‘1’denoting a bit indicating the presence of an ABS sub-frame, and ‘0’otherwise. For the case of Frequency Division Duplex (FDD) mode, thebitmap has a length of 40 bits, spanning 4 radio frames, with thepattern repeating every 4 radio frames. The length of 40 bits cancorrespond to a duty cycle periodicity of 40 ms.

In a specific embodiment, each eNB 16(1)-16(N) can use information(e.g., interference level, traffic load, and PDCCH duty cycle) obtainedfrom X2 message 22 as input parameters to calculate ABS resourceallocation at respective eNBs 16(1)-16(N). eNBs 16(1)-16(N) can also uselocal information (e.g., cell's own interference level, traffic load,assumed PDCCH duty cycle) as input parameters to calculate ABS resourceallocation at respective eNBs 16(1)-16(N).

According to various embodiments, the ABS resource allocation caninclude at least three parts: 1) exchange of resource allocation witheNBs in adjacent cells, which includes transmitting the eNB's ownresource allocation information and receiving corresponding informationfrom the eNB in the adjacent cells; 2) detection of collision inresource allocation between the eNBs; and 3) deriving and adjustingresource allocation to avoid or minimize resource collision whilemaximizing PDCCH in the local cell. In various embodiments, ABS modules20(1)-20(N) can provide a desirable trade-off between respective cellthroughput and protection of a level of PDCCH to neighboring cells.

In a general sense, the amount of resources allocated to the PDCCH canbe varied. However, if the allocated amount is too small, uplink anddownlink data schedulers may not be able to schedule all UEs in thecell, but if the allocated amount is too large, resources that couldhave been used for transmitting data are wasted. Moreover, if theneighboring cell schedules its UEs in sub-frames that overlap with theserving cell's ABS transmissions, the neighboring cell “protects” itsUEs from strong inter-cell interference, thereby improving the chancesof successful PDCCH reception by the UEs.

According to various embodiments, PDCCH interference from adjacent cellsmay be minimized (or avoided) in the serving cell (e.g., cell 14(1)).PDCCH interference can be prominent at the cell-edge UE 18, where thedifference in signal strengths arriving at the UE from multiple cells issmall. In some embodiments, ABS modules 20(1)-20(N) may execute analgorithm to define the ABS pattern, which can then be exchanged betweenrespective eNBs 16(1)-16(N). In one example embodiment, the ABSinformation of the load Information message of X2AP can be used in X2message 22 to carry the temporal location of ABS (e.g., ABS pattern).

Embodiments of communication system 10 can provide a framework toperform an optimal ABS allocation such that the impact of interferencefrom the neighboring cells on PDCCH is minimized. Also, the frameworkcan allow eNBs 16(1)-16(N) to balance own cell performance on one hand,and protection of the neighboring PDCCH on the other hand. In an exampleembodiment, the balance may be achieved by adaptively adjusting amaximum number of ABSs used. By decreasing the maximum number of ABSs,more sub-frames can be used for carrying data via PDSCH at the expenseof more PDCCH interference to the neighboring eNBs. On the other hand,increasing the maximum number of ABSs provides more PDCCH to theneighboring eNBs at the expense of the eNB's own throughput.

Embodiments of communication system 10 can facilitate deriving optimaltemporal location of the ABS by considering ABS information receivedfrom neighboring cells. The ABS allocation framework according to theembodiments allows eNBs 16(1)-16(N) to consider relative impact ofneighboring cells, and increase efficiency of ABS pattern selection. Insome embodiments, the ABS allocation framework allows flexibility todefine a maximum PDCCH duty cycle (which can be an inverse of the ABSduty cycle) within a given time duration to facilitate a pre-definedtrade-off between cell throughput and level of PDCCH protection for theneighboring cells.

Embodiments of communication system 10 can derive an optimal temporallocation of the ABS (e.g., ABS pattern) by minimizing contention of ABSsacross multiple neighboring cells 14(1)-14(N). PDCCH interference acrossmultiple adjacent cells 14(1)-14(N) may be reduced with potentialimprovement in signal quality. Overall PDCCH signal quality to UE 18(and other UEs in network 12) may be improved under the coverage area,with additional benefit to the cell-edge UEs (e.g., UE 18) where thesignal degradation and interference is usually higher than cell-centerUEs. Embodiments of communication system 10 can improve cell widecontrol signal quality between cell-centers and cell-edges. Thereliability of control plane signaling can be improved, with potentialimprovement in overall call quality and user experience.

From a commercial point of view, embodiments of communication system 10can reduce impact of inter-cell interference on the PDCCH of theneighboring cells, potentially enhancing accuracy of receptions of thedownlink control channels by UEs. As probability of correct decoding ofthe control channel improves, probability of dropped calls may bereduced. Such performance improvement may have a direct impact on thenetwork operator's business, allowing the network operator to define asoft tradeoff between own cell throughput and PDCCH protection level ofthe neighboring cells with consequent additional potential for networkoptimization and tuning. According to some embodiments, a more flexiblecell deployment may be facilitated, for example, by allowing serving eNB16(1) to measure and decide which neighboring cells have higherinterference impact autonomously and subsequently select the ABS patterndynamically in order to minimize the impact towards the impactedneighboring cells.

Embodiments of communication system 10 may be implemented inheterogeneous networks and homogeneous networks, including macrocell/pico (or femto) cell, small cell/small cell and micro cell/microcell deployments. In embodiments wherein macro, pico, and femto cellsare active within a common geographical area, the offending macro andfemto cells may both require use of ABS sequences, wherein the optimalABS sequence selection as described herein can be used between the macroand femto cells. Embodiments of communication system 10 may specify away of performing ABS resource allocation optimally such that thepotentially impact of the neighboring cells is considered individually.Thus, the temporal allocation of the ABSs can be steered towards cellsthat potentially experience the most impact (e.g., in crowded areas, orheavily trafficked areas), thereby increasing the effectiveness of theallocation. In addition, embodiments of communication system 10 allowthe duty-cycle of the ABS within a fixed time duration to besemi-statically adjusted, for example, to provide a desirable trade-offbetween own cell throughput and level of PDCCH protection to theneighboring cells.

In embodiments including HetNet, network 12 may comprise macrocells andpicocells, which are randomly deployed within each macrocell. One of themain challenges is interference management between the macrocell andpicocell, corresponding to a cross-tier interference problem specific tothe co-channel HetNet deployment. In LTE-Advanced networkingtechnologies, it is possible for a picocell to extend its range byadjusting the UE measurement bias, thereby making the picocell moreattractive from the UEs' perspective. The extended range is commonlyknown as Cell Range Extension (CRE). However, UEs within CRE region ofthe picocell would typically experience a higher interference in thedownlink from the macrocell. In this context, the macrocell is known asthe aggressor, and the picocell is considered as the victim cell.

Due to the higher interference, the performance of the CRE UEs would bebenefited if the picocell eNB (PeNB) can transmit to the UEs when themacro cell is in ABSs. Let R_(i,p) ⁽¹⁾ and R_(i,p) ⁽²⁾ the average bitrate per subframe achievable by UE i, in picocell p in the CRE andnon-CRE region respectively. Let S_(p) ⁽¹⁾ and S_(p) ⁽²⁾ be the set ofUEs within picocell p within CRE and non-CRE region respectively.Furthermore, let N⁽¹⁾ and N⁽²⁾ be the number of ABS and non-ABSsubframes respectively. The ratio η_(p) of average bit rate achievableby UEs in the CRE region to those in the non-CRE region can be expressedas

$\eta_{p} = \frac{\frac{N^{(1)}}{S_{p}^{(1)}}{\sum\limits_{i \in S_{p}^{(1)}}R_{i,p}^{(1)}}}{\frac{N^{(2)}}{S_{p}^{(2)}}{\sum\limits_{i \in S_{p}^{(2)}}R_{i,p}^{(2)}}}$where |S_(p) ⁽¹⁾| and |S_(p) ⁽²⁾| correspond to the number of UEs withinthe sets S_(p) ⁽¹⁾ and S_(p) ⁽²⁾ respectively. In other words, theformula above compares the relative performance (i.e. aggregate datarate at the cell level) in both CRE (cell-edge) and non-CRE(cell-center) regions. Based on η_(p), the PeNB can compute a “happinessindicator” ρ_(p) such that

$\rho_{p} = \left\{ \begin{matrix}1 & {{{if}\mspace{14mu}\eta_{p}} \leq \overset{\sim}{\eta_{P}}} \\0 & {otherwise}\end{matrix} \right.$where η_(p) is a threshold. The level of “happiness” increases at thepico cell if the aggregate UE performance at the CRE area increases,dependent on the number of ABS frames used by the dominant macrocell.Note that the above is expressed in discrete value. To provide a moredescriptive representation of the “happiness”, it is possible to expressthe happiness indicator as a continuously changing variable. Forexample, an alternative representation of ρ_(p) can be expressed as

$\begin{matrix}{\rho_{p} = {\min\left( {B,\frac{\overset{\sim}{\eta_{P}}}{\eta_{p}}} \right)}} & \;\end{matrix}$where the quantity B is a constant to limit the value of the ratio.

Subsequently, PeNB will then send ρ_(p) to its macro neighbor(s) eNBsthat have a considerable interference impact to the sending PeNB. Uponreceiving the quantity ρ_(p), the macro eNB (MeNB) would then lower orincrease the number of ABS subframes to adjust the level of picocellprotection. More generally, the average rates R_(i,p) ⁽¹⁾ and R_(i,p)⁽²⁾ in the above ratio η_(p) can be replaced by general utilityfunctions U_(i,p) ⁽¹⁾(R_(i,p) ⁽¹⁾) and U_(i,p) ⁽²⁾(R_(i,p) ⁽²⁾), whichare typically (but not necessarily limited to) a concave function suchas a logarithmic function log_(p) χ.

In various embodiments, serving eNB 16(1) may determine dominantneighboring eNBs (e.g., neighboring eNBs most likely to causesignificant interference) in its vicinity. In one example embodiment,UEs (e.g., UE 18) of serving cell 14(1) can be instructed to measure areference signal received power (RSRP) of neighboring cells and reportback to serving cell eNB 16(1). (RSRP is a basic UE physical layermeasurement and is a linear average (in watts) of downlink referencesignals (RS) across a channel bandwidth. The RS exists only for onesymbol at a time, therefore the RSRP measurement is made only on thoseREs that contain cell-specific RS. RSRP provides the UE with essentialinformation about strength of cells from which path loss can becalculated.) Neighboring cells with an aggregated path loss below acertain threshold can be added to a dominant neighbor list at servingeNB 16(1) for PDCCH ICIC purposes. Path loss (or path attenuation) isthe reduction in power density (attenuation) of an electromagnetic waveas it propagates through space.

In another embodiment, serving eNB 16(1) can find the RS powerinformation from system information block (SIB) 2. (Typically,cell-specific RS are embedded in an overall signal bandwidth at certainREs. For example, in the frequency domain, every 6th subcarrier carriesa RS. In the time domain, every 4th symbol carries the RS symbols. TheRS pattern can be a pseudo-random sequence, whose generation depends onthe cell's identity and cyclic prefix. The RS can be found by decodingSIB 2 from various eNBs.) The combination of the RS information fromneighboring eNBs can be used to obtain path loss between the UEs withrespect to neighboring cells 14(2)-14(N). For each neighboring cell14(2)-14(N), the path loss information can be aggregated among allreporting UEs at serving cell 14(1). Neighboring eNBs with an aggregatedpath loss below a certain threshold can be added to the dominantneighbor list for PDCCH ICIC purposes.

Based on information exchange in X2 message 22 (received from eachneighboring eNB 16(2)-16(N)), the ABS patterns of dominant neighboringeNBs 16(2)-16(N) may be known by eNB 16(1). According to an embodimentof communication system 10, the ABS pattern in the frames may bedetermined as follows. For each sub-frame, an aggregate impact ofinterference due to the neighboring eNBs 16(2)-16(N) may be calculatedat serving eNB 16(1). Based on X2 message 22, eNB 16(1) may know whethereach of the neighboring eNBs 16(2)-16(N) can transmit at a certainsub-frame. Serving eNB 16(1) can calculate a total number of neighboringeNBs who can transmit at each sub-frame. Serving eNB 16(1) may attemptto find P sub-frames at which a least number of neighboring eNBs cantransmit.

However, selecting the sub-frames may not take into account the relativeimpact of each of the transmitting neighboring eNBs 16(2)-16(N). Forexample, even when two neighboring eNBs (say eNB 16(2) and 16(N))declare to transmit at sub=frame i, if one neighboring eNB (e.g., eNB16(N)) is geographically located farther from serving eNB 16(1) than thesecond neighboring eNB (e.g., eNB 16(2)), the relative impact of thefirst neighboring eNB (e.g., eNB 16(N)) compared to the secondneighboring eNB (e.g., eNB 16(2)) on interference at serving eNB 16(1)may be smaller.

According to some other embodiments, a weight may be assigned to eachneighboring eNB 16(2)-16(N) by serving eNB 16(1) for each sub-frame. Anysuitable method for assigning weights may be used within the broad scopeof the embodiments. Each sub-frame may be selected based on a sum ofweights corresponding to neighboring eNBs 16(2)-16(N) who declare thatthey can transmit at the sub-frame. A probability of selecting eachsub-frame for generating the ABS pattern may be called the sub-frame's“selectability.” After collecting the selectability of each sub-framefor ABS patterns for substantially all neighboring eNBs 16(2)-16(N),serving eNB 16(1) may select P sub-frames having the least impact fromneighboring eNBs 16(2)-16(N).

In various embodiments, assigning the weights may include consideringvarious network parameters, including: (1) received RSRP at a networkmonitor mode (NMM) of serving eNB 16(1) from neighboring eNBs16(2)-16(N) (an NMM is a receiver geographically located at a locationof serving eNB 16(1), and is used to sense the network environment. Itsbehavior is similar to a UE receiver); (2) transmit RS power at the NMMof serving eNB 16(1) from neighboring eNBs 16(2)-16(N) (the transmit RSpower can be obtained from the SIB2 of neighboring eNBs 16(2)-16(N));(3) received RSRP at the UE receivers from neighboring eNBs16(2)-16(N)); (4) transmit RS power (e.g., obtained from SIB2) at theUEs from neighboring eNBs 16(2)-16(N); (5) path losses between eNB 16(1)and each of neighboring eNBs 16(2)-16(M) (e.g., path losses may becalculated based on received RSRP and transmit RS power from neighboringeNBs 16(2)-16(N) at eNB 16(1); for example, path loss can be computed asa difference between RSRP and transmit RS power in dB); (6) path lossesbetween each of the connected UEs and each neighboring eNB 16(2)-16(N)(e.g., path losses can be computed based on received RSRP and RS powerfrom neighboring eNBs 16(2)-16(N) at the UE); (7) traffic load of eachneighboring eNB 16(2)-16(N).

In mathematical terms, let x_(i,m) be a binary digit (e.g., 0, 1) with‘1’ denoting that the PDCCH is active in sub-frame m for cell i, andzero otherwise, where 1≤m≤M (M being any integer representing themaximum number, e.g., 10, of sub-frames in a frame). An active PDCCH canimply that the sub-frame is not an ABS. Let x_(i)=(x_(i,1), x_(i,2), . .. , x_(i,M)) be a bit sequence used by cell i, 1≤i≤N. The bit sequencex_(i) can be obtained at serving cell j based on two sources ofinformation: 1) ABS information IE in the X2AP Load information messagefrom neighboring cells that provides the ABS sub-frames to serving cellj; and 2) the Usable ABS Pattern Bitmap within the X2AP Resource StatusUpdate message that provides the set of ABSs that correspondingneighboring cells use.

Let S_(j) be the set of neighboring cells for serving cell j∉S_(j). TheABS selectability can be reduced to selecting x_(j) as follows:

$\min\limits_{x_{j}}\left( {\sum\limits_{\underset{j \notin S_{j}}{i \in S_{j}}}{a_{i}{\sum\limits_{m = 1}^{M}\;{x_{i,m}x_{j,m}}}}} \right)$subject to

${\sum\limits_{m = 1}^{M}x_{j,m}} = N_{j}^{(\max)}$where N_(j) ^((max)) is the maximum duty cycle of sub-frames with PDCCH(e.g., non-ABS sub-frames) for cell j, and a_(i), i∈S_(j) is aneighbor-specific weight that quantifies a relative level of impact fromcell i to serving cell j. The weight can be based on the impact ofinterference, which can be computed based on, but not limited to,dominant neighbor selection process.

The computational procedure to select x_(j) is as follows: (1) for eachm, compute a weighted sequence X_(m):

$X_{m} = {\sum\limits_{\underset{j \notin S_{j}}{i \in S_{j}}}{a_{i}x_{i,m}}}$

Rank the set {X_(m), m=1, 2, . . . M} such that X₍₁₎≤X₍₂₎≤ . . .≤X_((m))≤ . . . ≤X_((M)). Note that the sub-frame index corresponding toX_((m)) is no longer m. Define Q_(j) to be a set of sub-frame indicescorresponding to the sub-frame indices of {X₍₁₎, X₍₂₎, . . . , X_((N)_(j) _((max)) ₎}; set x_(j,m)=1 if m∈Q_(j), and x_(j,m)=0 otherwise.

Note also that the value of N_(j) ^((max)) can be adaptive, depending ona number of factors. One such factor may include general satisfactionwith the throughput performance. As N_(j) ^((max)) is reduced, thenumber of sub-frames available for ABS is higher. Thus, thecell-satisfaction such as the throughput can be continuously monitored.If the throughput is below a certain threshold over a pre-defined timeperiod, N_(j) ^((max)) can be increased. Adjustment of the maximum PDCCHduty cycle can allow a level of orthogonalization to be flexible anddynamic. In some embodiments, a level of radio link failure, energysaving (e.g., based on a number of connected UEs), and handover failurecan be monitored. When the radio link and/or handover failure are abovea certain threshold, serving eNB 16(j) can send a “request” message toits dominant neighboring eNBs to make a suggestion to lower the value ofN_(j) ^((max)). In some embodiments when a number of connected UEs fallsbelow a certain threshold, the maximum duty cycle in the cell may bereduced to save energy by transmitting less often.

In various embodiments, eNB 16(1) can semi-statically (e.g.,semi-dynamically) change the value of N₁ ^((max)), the maximum dutycycle of sub-frames with PDCCH for cell 14(1). Each eNB 16(1)-16(N) canadjust its own maximum PDCCH duty cycle value depending on local trafficdemand (e.g. number of UEs camped on a cell, hysteresis of past timeperiods, time of day, estimated traffic, etc.) and other suitablefactors. Also, serving eNB 16(1) can take into account a Resource StatusUpdate information from neighboring eNBs 16(2)-16(N). In variousembodiments, each neighboring eNB 16(2)-16(N) may behave in a morecooperative (e.g., less greedy) manner by lowering respective maximumduty cycle values, thus allowing serving cell 14(1) to have moreavailable resources for PDCCH allocation.

Turning to the infrastructure of communication system 10, the networktopology of network 12 can include any number of UEs, eNBs, switches androuters, and other nodes inter-connected to form a large and complexnetwork. A node may be any electronic device, client, server, peer,service, application, or other object capable of sending, receiving, orforwarding information over communications channels in a network.Elements of FIG. 1 may be coupled to one another through one or moreinterfaces employing any suitable connection (wired or wireless), whichprovides a viable pathway for electronic communications. Additionally,any one or more of these elements may be combined or removed from thearchitecture based on particular configuration needs.

Communication system 10 may include network configurations capable ofTCP/IP communications for the electronic transmission or reception ofdata packets in a network. Communication system 10 may also operate inconjunction with a User Datagram Protocol/Internet Protocol (UDP/IP) orany other suitable protocol, where appropriate and based on particularneeds. In addition, gateways, routers, switches, and any other suitablenodes (physical or virtual) may be used to facilitate electroniccommunication between various nodes in network 12.

The example network environment may be configured over a physicalinfrastructure that may include one or more networks and, further, maybe configured in any form including, but not limited to, cellularnetworks, local area networks (LANs), wireless local area networks(WLANs), VLANs, metropolitan area networks (MANs), wide area networks(WANs), Intranet, Extranet, any other appropriate architecture orsystem, or any combination thereof that facilitates communications in anetwork. In some embodiments, a communication link may represent anyelectronic link supporting a LAN environment such as, for example,cable, Ethernet, wireless technologies (e.g., IEEE 802.11x), ATM, fiberoptics, power-line, etc. or any suitable combination thereof. In otherembodiments, communication links may represent a remote connectionthrough any appropriate medium (e.g., digital subscriber lines (DSL),telephone lines, T1 lines, T3 lines, wireless, radio, satellite, fiberoptics, cable, Ethernet, etc. or any combination thereof) and/or throughany additional networks such as a wide area networks (e.g., theInternet).

The techniques described herein may be used in any OFDM network,including, by way of examples and not as limitations, cable-basednetworks (e.g., Asymmetric digital subscriber line (ADSL) andVery-high-bit-rate digital subscriber line (VDSL) broadband access viacopper wiring; Digital Video Broadcasting-Cable (DVB-C2); Power linecommunication (PLC); ITU-T G.hn standard for high-speed local areanetworking of existing home wiring; etc.) and wireless networks (e.g.,wireless LAN (WLAN) radio interfaces IEEE 802.11a, g, n, ac andHIPERLAN/2; digital radio systems DAB/EUREKA 147, DAB+, Digital RadioMondiale, HD Radio, T-DMB and ISDB-TSB; terrestrial digital TV systemsDVB-T and ISDB-T; terrestrial mobile TV systems DVB-H, T-DMB, ISDB-T;wireless personal area network (PAN) ultra-wideband (UWB) IEEE 802.15.3aimplementation; 4G and pre-4G cellular networks and mobile broadband,including IEEE 802.16e (or Mobile-WiMAX), mobile broadband wirelessaccess (MBWA) standard IEEE 802.20).

The techniques described herein may be used for various wirelesscommunication networks including frequency division duplexing (FDD) andtime division duplexing (TDD) of orthogonal frequency-division multipleaccess (OFDMA) (e.g., LTE and similar technologies) and that can alsoinclude other wireless technologies (e.g., in hybrid scenarios), such ascode division multiple access (CDMA), time division multiple access(TDMA), frequency division multiple access (FDMA), OFDMA, single carrierfrequency-division multiple access (SC-FDMA), etc. The CDMA network mayimplement a radio technology, such as UTRA, Telecommunications IndustryAssociation's (TIA's) CDMA2000®, and the like. The UTRA technologyincludes Wideband CDMA (WCDMA) and other variants of CDMA. The CDMA2000®technology includes the IS-2000, IS-95 and IS-856 standards from theElectronics Industry Alliance (EIA) and TIA.

A TDMA network may implement a radio technology, such as Global Systemfor Mobile Communications (GSM). An OFDMA network may implement a radiotechnology, such as Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB),IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, andthe like. The UTRA and E-UTRA technologies are part of Universal MobileTelecommunication System (UMTS). 3GPP LTE and LTE-Advanced (LTE-A) arenewer releases of the UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE,LTE-A and GSM are described in 3GPP documents. CDMA2000® and UMB aredescribed in 3GPP2 documents. The techniques described herein may beused for the wireless networks and radio access technologies mentionedabove, as well as other wireless networks and radio access technologies.

Note that the numerical and letter designations assigned to the elementsof FIG. 1 do not connote any type of hierarchy; the designations arearbitrary and have been used for purposes of teaching only. Suchdesignations should not be construed in any way to limit theircapabilities, functionalities, or applications in the potentialenvironments that may benefit from the features of communication system10. It should be understood that communication system 10 shown in FIG. 1is simplified for ease of illustration.

In various embodiments, network 12 can include a general cellularnetwork. In other embodiments, network 12 can include an enterprisenetwork, for example, a cellular network operating within an enterprisecontext. In yet other embodiments, network 12 can include a wide areanetwork, and other types of wireless networks. In a general senses, UE18 may include any type of device capable of communicating according toOFDM protocols with eNBs 16(1)-16(N), including smart phones, laptops,tablets, sensors, servers, and appliances.

In various embodiments, eNBs 16(1)-16(N) can include any type ofsuitable network elements configured to perform the ABS operations andother 3GPP functionalities described herein. As used herein, the term“network element” is meant to encompass computers, network appliances,servers, routers, switches, gateways, bridges, load-balancers,firewalls, processors, modules, or any other suitable device, component,element, or object operable to exchange information in a networkenvironment. Moreover, the network elements may include any suitablehardware, software, components, modules, interfaces, or objects thatfacilitate the operations thereof. This may be inclusive of appropriatealgorithms and communication protocols that allow for the effectiveexchange of data or information.

eNBs 16(1)-16(N) comprise hardware connected to network 12 thatcommunicates directly with UE 18, for example similar to a basetransceiver station (BTS) in GSM networks, and are responsible forsubstantially all radio related functions (e.g., radio resourcemanagement, header compression, security, etc.). eNBs 16(1)-16(N) mayembed their own control functionality, or may use a radio networkcontroller within the broad scope of the embodiments. eNBs 16(1)-16(N)can include one or more chips (e.g., chipset) configured to providemobile data transfer services according to LTE protocols. eNBs16(1)-16(N) may be interconnected with each other and with other networkelements by suitable interfaces (e.g., with each other by the X2interface; to an MME by a S1-MME interface; and to an S-GW by a S1-Uinterface; etc.).

Turning to FIG. 2, FIG. 2 is a simplified block diagram illustratingexample details of an embodiment of communication system 10. An exampleeNB 16 may include ABS module 20, comprising a processor 22 and a memoryelement 24, among other components. A dominant neighbor selection module26 may receive network parameters 28 from UEs and neighboring eNBs andgenerate a dominant neighbor list 30. Dominant neighbor list 30 maycomprise any suitable table, array, list, or other storage elementsuitable for storing identifiers of neighboring eNBs and correspondingnetwork parameters 28. Network parameters 28 may include parametersindicative of path loss between eNB 16 and neighboring eNBs, andparameters used to recognize ABS patterns used by neighboring eNBs,PDCCH duty cycles of neighboring eNBs, and other information that can beused in calculating eNB 16's optimal ABS pattern. Network parameter 28may be aggregated, extracted, identified, etc. from X2 messages sent byneighboring eNBs, measurement reports by UEs, NMM measurements, etc. AnABS pattern calculator 32 may determine an ABS pattern 34 based ondominant neighbor list 30 and corresponding ABS information ofneighboring eNBs and a (PDCCH) duty cycle 36, calculated at a duty cycleestimator 38. ABS pattern 34 may be inserted by an X2 message module 40into X2 message 22 and transmitted to neighboring eNBs.

Turning to FIG. 3, FIG. 3 is a simplified block diagram illustratingexample details of an embodiment of communication system 10. eNB 16(1)may send X2 message 22 comprising load information to eNB 16(2). X2message 22 comprising load information may include an ABS information IE42 comprising an ABS pattern 44. In many embodiments, X2 message 22 maysubstantially comply with X2AP specifications of 3GPP.

Turning to FIG. 4, FIG. 4 is a simplified block diagram illustratingexample details of a frame structure of E-UTRAN air interface used inLTE according to an embodiment of communication system 10. Frames 50(1)and 50(2) in cell A 14(1) and cell B 14(2) may comprise several (e.g.,10) sub-frames (e.g., indexed from 0 to 9). A detail of frame 50(1) inan inset indicates sub-frames (SF) 52(1)-52(10) indexed as SF1, SF2, . .. SF10. Each sub-frame (e.g., SF4 in the inset) may include a controlregion 54 and a data region 56. A value of “0” for an appropriate regionof control region 54 may indicate that the ABS has been allocated forthe sub-frame, and a value of 1 for the appropriate region of controlregion 54 may indicate that the ABS has not been allocated for thesub-frame. Sub-frames 1, 2, and 5 in frame 50(1) and sub-frames 3, 4 and6 in frame 50(2) are configured as ABS in this example. Note that theABS pattern configured in cell A 14(1) and cell B 14(2) can becommunicated to neighboring cells via the X2 interface.

Turning to FIG. 5, FIG. 5 is a simplified flow diagram illustratingexample operations 100 that may be associated with embodiments ofcommunication system 10. At 102, a timer T may be set to N (any suitablenumber). A suitable PDCCH duty cycle N_(j) ^((max)) may be selected atserving eNB j, for example, taking into account traffic patterns, cellload, X2AP resource status update message from neighboring eNBs, etc. At104, the serving eNB j may receive ABS information from neighboringeNBs. At 106, the serving eNB j may compute an optimal ABS pattern atthe selected PDCCH duty cycle N_(j) ^((max)). At 108, the computed ABSpattern may be assigned to the frame, and neighboring eNBs may beinformed about the assigned ABS pattern. At 110, a determination may bemade whether the timer T has reduced to 0. If not, the timer may bedecremented by 1 at 112, and the operations may loop back to 104. If thetimer has reduced to zero, the operations may be reset, and start anewat 102.

Turning to FIG. 6, FIG. 6 is a simplified flow diagram illustratingexample operations 120 that may be associated with embodiments ofcommunication system 10. At 122, serving eNB 16(1) may receive networkparameters 28 from neighboring eNBs 16(2)-16(N). At 124, the dominantneighboring eNBs may be identified. At 126, a sub-frame index may be setto 1. At 128, a neighboring eNB in dominant neighbor list 30 may beselected. At 130, a neighbor count for the sub-frame may be set to 0. At132, a determination may be made whether the selected neighboring eNBtransmits at the currently selected sub-frame (e.g., sub-frame 1 in theinitial iteration). At 134, if the neighboring eNB transmits at thecurrently selected sub-frame, neighbor count for the sub-frame may beincremented by 1. At 136, a determination may be made whether moreneighboring eNBs are listed in dominant neighbor list 30. If moreneighboring eNBs are listed in dominant neighbor list 30, at 138, a nextneighboring eNB in dominant neighbor list 30 may be selected, and theoperations may loop back to 132. If the neighboring eNB does nottransmit at the currently selected sub-frame, the operations may step to136.

If more neighboring eNBs are not listed in dominant neighbor list 30, at140, a determination may be made whether more sub-frames are present inthe frame. If more sub-frames are present in the frame, at 142, a nextsub-frame in the frame may be selected, for example, by choosing thesub-frame with the next higher sub-frame index. The operations may loopback to 128. If more sub-frames are not present in the frame at 140,sub-frames having low neighbor count may be identified at 144. At 146,the identified sub-frames may be used (e.g., configured) for ABS.

Turning to FIG. 7, FIG. 7 is a simplified flow diagram illustratingexample operations 150 that may be associated with embodiments ofcommunication system 10. At 152, the serving eNB may receive networkparameters 28. At 154, dominant neighboring eNBs may be identified. At156, weights may be set (e.g., assigned) for each neighboring eNB, forexample, based on a probability of higher interference from thatneighboring eNB. A neighboring eNB with higher probability ofinterference (e.g., due to proximity, higher transmit power, etc.) maybe assigned a higher weight. At 158, computation parameters (e.g.,sub-frame index, neighbor count, etc.) may be initialized. At 160,sub-frames used by each neighboring eNB may be identified. At 162,sub-frames based on a sum of weights corresponding to neighboring eNBsmay be selected. At 164, the identified sub-frames may be selected forABS.

Turning to FIG. 8, FIG. 8 is a simplified flow diagram illustratingexample operations 170 that may be associated with embodiments ofcommunication system 10. At 172, a maximum duty cycle for sub-frameswith PDCCH (e.g., non-ABS sub-frames) may be set (e.g., initialized) atserving eNB 16(1). At 174, the ABS pattern may be determined subject tothe maximum duty cycle constraint. At 176, cell throughput at servingcell 14(1) may be monitored. At 178, a determination may be made whetherthe cell throughput is less than a pre-configured threshold. If not, theoperations may loop back to 176, and continue. If the cell throughput isless than the pre-configured threshold, the maximum duty cycle may beadjusted (e.g., increased) at 180. The operations may revert back to174, and continue thereafter.

Turning to FIG. 9, FIG. 9 is a simplified flow diagram illustratingexample operations 190 that may be associated with embodiments ofcommunication system 10. At 192, a maximum duty cycle for sub-frameswith PDCCH (e.g., non-ABS sub-frames) may be set (e.g., initialized) atserving eNB 16(1). At 194, the ABS pattern may be determined subject tothe maximum duty cycle constraint. At 196, the radio link and/orhandover failure at serving cell 14(1) may be monitored. At 198, adetermination may be made whether the radio link and/or handover failureis greater than a pre-configured threshold. If not, the operations mayloop back to 196, and continue. If the radio link and/or handoverfailure is greater than the pre-configured threshold, a request may besent to the relevant neighboring eNBS 16(2)-16(N) to adjust (e.g.,increase) their respective maximum duty cycle at 200. The operations mayrevert back to 194, and continue thereafter.

Note that in this Specification, references to various features (e.g.,elements, structures, modules, components, steps, operations,characteristics, etc.) included in “one embodiment”, “exampleembodiment”, “an embodiment”, “another embodiment”, “some embodiments”,“various embodiments”, “other embodiments”, “alternative embodiment”,and the like are intended to mean that any such features are included inone or more embodiments of the present disclosure, but may or may notnecessarily be combined in the same embodiments.

Note also that an ‘application’ as used herein this Specification, canbe inclusive of an executable file comprising instructions that can beunderstood and processed on a computer, and may further include librarymodules loaded during execution, object files, system files, hardwarelogic, software logic, or any other executable modules. Furthermore, thewords “optimize,” “optimization,” “optimal” and related terms are termsof art that refer to improvements in speed and/or efficiency of aspecified outcome and do not purport to indicate that a process forachieving the specified outcome has achieved, or is capable ofachieving, an “optimal” or perfectly speedy/perfectly efficient state.

In example implementations, at least some portions of the activitiesoutlined herein may be implemented in software in, for example, eNB 16.In some embodiments, one or more of these features may be implemented inhardware, provided external to these elements, or consolidated in anyappropriate manner to achieve the intended functionality. The variousnetwork elements (e.g., eNBs, UEs) may include software (orreciprocating software) that can coordinate in order to achieve theoperations as outlined herein. In still other embodiments, theseelements may include any suitable algorithms, hardware, software,components, modules, interfaces, or objects that facilitate theoperations thereof.

Furthermore, eNB 16 described and shown herein (and/or their associatedstructures) may also include suitable interfaces for receiving,transmitting, and/or otherwise communicating data or information in anetwork environment. Additionally, some of the processors and memoryelements associated with the various nodes may be removed, or otherwiseconsolidated such that a single processor and a single memory elementare responsible for certain activities. In a general sense, thearrangements depicted in the FIGURES may be more logical in theirrepresentations, whereas a physical architecture may include variouspermutations, combinations, and/or hybrids of these elements. It isimperative to note that countless possible design configurations can beused to achieve the operational objectives outlined here. Accordingly,the associated infrastructure has a myriad of substitute arrangements,design choices, device possibilities, hardware configurations, softwareimplementations, equipment options, etc.

A logical representation, such as those described herein, represents anabstract view of a network or network element by means of informationobjects representing network elements, aggregations of network elements,the topological relationship between the network elements, endpoints ofconnections (e.g., termination points), and transport entities (e.g.,connections) that transport information between two or more terminationpoints. The information objects defined in the logical representationare used, among others, by connection management functions. In this way,a physical implementation independent management can be achieved.

In some of example embodiments, one or more memory elements (e.g.,memory element 24) can store data used for the operations describedherein. This includes the memory element being able to storeinstructions (e.g., software, logic, code, etc.) in non-transitorymedia, such that the instructions are executed to carry out theactivities described in this Specification. A processor can execute anytype of instructions associated with the data to achieve the operationsdetailed herein in this Specification. In one example, processors (e.g.,processor 22) could transform an element or an article (e.g., data) fromone state or thing to another state or thing. In another example, theactivities outlined herein may be implemented with fixed logic orprogrammable logic (e.g., software/computer instructions executed by aprocessor) and the elements identified herein could be some type of aprogrammable processor, programmable digital logic (e.g., a fieldprogrammable gate array (FPGA), an erasable programmable read onlymemory (EPROM), an electrically erasable programmable read only memory(EEPROM)), an ASIC that includes digital logic, software, code,electronic instructions, flash memory, optical disks, CD-ROMs, DVD ROMs,magnetic or optical cards, other types of machine-readable mediumssuitable for storing electronic instructions, or any suitablecombination thereof.

These devices may further keep information in any suitable type ofnon-transitory storage medium (e.g., random access memory (RAM), readonly memory (ROM), field programmable gate array (FPGA), erasableprogrammable read only memory (EPROM), electrically erasableprogrammable ROM (EEPROM), etc.), software, hardware, or in any othersuitable component, device, element, or object where appropriate andbased on particular needs. The information being tracked, sent,received, or stored in communication system 10 could be provided in anydatabase, register, table, cache, queue, control list, or storagestructure, based on particular needs and implementations, all of whichcould be referenced in any suitable timeframe. Any of the memory itemsdiscussed herein should be construed as being encompassed within thebroad term ‘memory element.’ Similarly, any of the potential processingelements, modules, and machines described in this Specification shouldbe construed as being encompassed within the broad term ‘processor.’

It is also important to note that the operations and steps describedwith reference to the preceding FIGURES illustrate only some of thepossible scenarios that may be executed by, or within, the system. Someof these operations may be deleted or removed where appropriate, orthese steps may be modified or changed considerably without departingfrom the scope of the discussed concepts. In addition, the timing ofthese operations may be altered considerably and still achieve theresults taught in this disclosure. The preceding operational flows havebeen offered for purposes of example and discussion. Substantialflexibility is provided by the system in that any suitable arrangements,chronologies, configurations, and timing mechanisms may be providedwithout departing from the teachings of the discussed concepts.

Although the present disclosure has been described in detail withreference to particular arrangements and configurations, these exampleconfigurations and arrangements may be changed significantly withoutdeparting from the scope of the present disclosure. For example,although the present disclosure has been described with reference toparticular communication exchanges involving certain network access andprotocols, communication system 10 may be applicable to other exchangesor routing protocols. Moreover, although communication system 10 hasbeen illustrated with reference to particular elements and operationsthat facilitate the communication process, these elements, andoperations may be replaced by any suitable architecture or process thatachieves the intended functionality of communication system 10.

Numerous other changes, substitutions, variations, alterations, andmodifications may be ascertained to one skilled in the art and it isintended that the present disclosure encompass all such changes,substitutions, variations, alterations, and modifications as fallingwithin the scope of the appended claims. In order to assist the UnitedStates Patent and Trademark Office (USPTO) and, additionally, anyreaders of any patent issued on this application in interpreting theclaims appended hereto, Applicant wishes to note that the Applicant: (a)does not intend any of the appended claims to invoke paragraph six (6)of 35 U.S.C. section 112 as it exists on the date of the filing hereofunless the words “means for” or “step for” are specifically used in theparticular claims; and (b) does not intend, by any statement in thespecification, to limit this disclosure in any way that is not otherwisereflected in the appended claims.

What is claimed is:
 1. A method, comprising: receiving, at a servingEvolved Universal Terrestrial Radio Access Network (E-UTRAN) nodeB(eNB), almost blank sub-frame (ABS) patterns from a plurality ofneighboring eNBs in an orthogonal frequency-division multiplexing (OFDM)based network, each neighboring eNB transmitting a separate ABS patternduring a time period, wherein the ABS patterns are received at theserving eNB from respective neighboring eNBs in messages, each of themessages comprising a bit sequence indicating a time-domain resourceallocation for each of the neighboring eNBs using a plurality of binarybits; comparing, at the serving eNB, the received ABS patterns with theserving eNB's resource allocation during the time period, the resourceallocation including cell-load and traffic demands at the serving eNB,wherein comparing the received ABS patterns comprises detecting alikelihood of a resource allocation collision with respect to one of theneighboring eNBs using the bit sequences; computing an optimal ABSpattern at the serving eNB based on the comparison at the serving eNB,wherein the optimal ABS pattern causes each neighboring eNB to adjustits own resource allocation to at least minimize the resource allocationcollision at the serving eNB; and after adjusting the resourceallocation of the serving eNB, sending the optimal ABS pattern to theplurality of neighboring eNBs, wherein each neighboring eNB adjusts arespective resource allocation according to the optimal ABS pattern toreduce interference.
 2. The method of claim 1, wherein the messagesconform to X2AP specifications over corresponding X2 interfaces.
 3. Themethod of claim 1, wherein the optimal ABS pattern is sent to theneighboring eNBs in another message conforming to X2AP specificationsover corresponding X2 interfaces.
 4. The method of claim 1, furthercomprising sending a request to a first neighboring eNB of theneighboring eNBs when at least one of a radio link failure and ahandover failure with the first neighboring eNB is above a preconfiguredthreshold, wherein the request indicates adjusting a maximum duty cycleat the first neighboring eNB.
 5. The method of claim 4, furthercomprising adjusting the maximum duty cycle when a cell throughput atthe serving eNB falls below a preconfigured threshold.
 6. The method ofclaim 1, wherein the optimal ABS pattern balances a trade-off betweenthe serving eNB's cell performance and protection of neighbor PDCCH. 7.The method of claim 1, wherein signals arrive at a cell-edge userequipment (UE) from multiple cells, wherein a difference in signalstrength between the signals is small.
 8. Non-transitory tangible mediathat includes instructions for execution, which when executed by aprocessor, is operable to perform operations comprising: receiving, at aserving eNB, ABS patterns from a plurality of neighboring eNBs in anOFDM based network, each neighboring eNB transmitting a separate ABSpattern during a time period, wherein the ABS patterns are received atthe serving eNB from respective neighboring eNBs in messages, each ofthe messages comprising a bit sequence indicating a time-domain resourceallocation for each of the neighboring eNBs using a plurality of binarybits; comparing, at the serving eNB, the received ABS patterns with theserving eNB's resource allocation during the time period, the resourceallocation including cell-load and traffic demands at the serving eNB,wherein comparing the received ABS patterns comprises detecting alikelihood of a resource allocation collision with respect to one of theneighboring eNBs using the bit sequences; setting a maximum duty cycleof physical downlink control channel (PDCCH) in a frame to betransmitted by the serving eNB within its serving cell; computing anoptimal ABS pattern at the serving eNB based on the comparison at theserving eNB, wherein the optimal ABS pattern causes each neighboring eNBto adjust its own resource allocation to at least minimize the resourceallocation collision at the serving eNB; and after adjusting theresource allocation of the serving eNB, sending the optimal ABS patternto the plurality of neighboring eNBs, wherein each neighboring eNBadjusts a respective resource allocation according to the optimal ABSpattern to reduce interference.
 9. The media of claim 8, wherein the ABSmessages conform to X2AP specifications over corresponding X2interfaces.
 10. The media of claim 9, wherein each of the messagescomprises a resource status update message, where the X2APspecifications are enhanced to include the respective ABS pattern in theresource status update message.
 11. The media of claim 9, wherein eachof the messages comprises a load information message, wherein therespective ABS pattern is included in an ABS pattern information bitmapwithin an ABS information element in the load information message. 12.An apparatus, comprising: a memory element for storing data; and aprocessor, wherein the processor executes instructions associated withthe data, wherein the processor and the memory element cooperate, suchthat the apparatus is configured for: receiving, at a serving eNB, ABSpatterns from a plurality of neighboring eNBs in an OFDM based network,each neighboring eNB transmitting a separate ABS pattern during a timeperiod, wherein the ABS patterns are received at the serving eNB fromrespective neighboring eNBs in messages, each of the messages comprisinga bit sequence indicating a time-domain resource allocation for each ofthe neighboring eNBs using a plurality of binary bits; comparing, at theserving eNB, the received ABS patterns with the serving eNB's resourceallocation during the time period, the resource allocation includingcell-load and traffic demands at the serving eNB, wherein comparing thereceived ABS patterns comprises detecting a likelihood of a resourceallocation collision with respect to one of the neighboring eNBs usingthe bit sequences; computing an optimal ABS pattern at the serving eNBbased on the comparison at the serving eNB, wherein the optimal ABSpattern causes each neighboring eNB to adjust its own resourceallocation to at least minimize the resource allocation collision at theserving eNB; and after adjusting the resource allocation of the servingeNB, sending the optimal ABS pattern to the plurality of neighboringeNBs, wherein each neighboring eNB adjusts a respective resourceallocation according to the optimal ABS pattern to reduce interference.13. The apparatus of claim 12, wherein the messages conform to X2APspecifications over corresponding X2 interfaces.
 14. The apparatus ofclaim 13, wherein each of the messages comprises a resource statusupdate message, where the X2AP specifications are enhanced to includethe respective ABS pattern in the resource status update message. 15.The apparatus of claim 13, wherein each of the messages comprises a loadinformation message, wherein the respective ABS pattern is included inan ABS pattern information bitmap within an ABS information element inthe load information message.